If you live in California, you’ve heard that you’re not supposed to surf after it rains. Apparently, all the filth we vomit out every day builds up, then runs into the ocean at an alarming rate. Crowd control at its finest and most disgusting. Recently, more than 600 surfers helped researchers look at exactly how disgusting it is.

The study was conducted by researchers at UC Berkley, the Southern California Coastal Water Research Project, and the Surfrider Foundation. Although it’s long been assumed that surfing after a rain isn’t all that good for you, there haven’t been all that many studies about exactly what is in the water and how much of it there is. Since there’s a definite lack of rain in Southern California, all the shit has more time to build up, and a deluge of bacteria like E. coli and Enterococcus flows into the ocean and into our mouths, ears, and open wounds.

The surfers, mostly from the San Diego County area, risked their health in the name of science for a free bar of wax and a subscription to an unnamed forecasting service. According to the LA Times, every time they surfed or got sick, they logged it on an app. Researchers recorded the data over the winters of 2013-2104 and 2014-2015 at Tourmaline and Ocean Beach. The average surfer went out two times a week for about two hours. Almost 40% reported that they swallowed water, while 96% dunked their heads–a pretty good percentage for a two-hour session. Here’s the strange part, though. The participants weren’t required to surf after it rained, so only about 10% of the data was considered to be “wet weather exposure.”

So here’s what they found: the more you surf, the more you get sick. “The risk of getting sick after swimming in the ocean is about 25 per 1,000. That number increases to 32 per 1,000 following rainy conditions,” Daniel Wheaton of the LA Times wrote. “Compared with non-surfing times, exposure to seawater increased the rates of infections and gastrointestinal illness, with wet weather increasing the risk even further.”

Here’s a thought, though: instead of surfing less, maybe we should stop pumping so much toxic shit into the environment.